1. Field of the Invention
The present invention relates to an apparatus for lifting, excavating, splitting and/or crushing tree stumps, or other materials. The apparatus is characterized in part by a two pivot point design.
2. Background
A number of mechanical devices have been developed for the crushing and demolition of a variety of materials, including wood. Certain of these devices utilize a frame having an upper and lower jaw for gripping and cutting the material or work product.
For example, U.S. Pat. No. 5,533,682 describes a device for crushing and/or cutting concrete, cutting iron sections and/or scrap iron, and cutting and splitting wood. The device comprises a frame having a first jaw that is stationary with respect to the frame, and a second jaw that is pivotable by means of a setting cylinder. While the fixed first jaw is intended to support the material being cut, the pivotable jaw includes a pointed crusher tooth and knife-like section that facilitate the cutting of the material.
This device offered some advantages over the art. For example, the jaws of the device were detachably connected to the frame, so that a different set of jaws could be used for different materials being cut. Thus, one device could be used for multiple purposes, as long as one purchased the appropriate sets of jaws.
However, this type of device presented certain limitations as a wood splitter and crusher. The particular embodiment described as being suited for cutting and splitting wood employed two serrated strips located on the inner surface of the fixed jaw to prevent slippage of the wood during the cutting process. While this design may be effective for cutting smaller sections of wood, logs, root ends and the like, when cutting larger sections of wood, e.g., tree stumps, forward slippage of the wood becomes highly problematic. Further, the force of the pivotable jaw upon the stationary jaw could lead to dislodgement or misalignment of one or more of the jaws with respect to the frame.
A similar device intended for use in the demolition of iron or steel reinforced concrete structures is disclosed in U.S. Pat. No. 5,146,683. This device, termed a reinforcement cutter, also employs a moveable upper jaw and a stationary lower jaw configuration. The device further includes a first and second shearing cutter means that are dismountably secured to each of the opposed inner lateral surfaces of the upper and lower jaws in a bent formation. As in the case above, however, the potential for forward slippage of the wood and/or dislodgement of one or more of the jaws is problematic when using this device for cutting and splitting large sections of wood.
Other devices for splitting and crushing tree stumps have been developed that utilize a bit/counter bit configuration.
Swedish patent publication 378,502 describes a splitting bit that is pressed between two counter bits. The counter bits are disposed at the adjacent upper edges of arm-like structures that support the tree stump, and have an arcuate shape that facilitates the holding of the stump.
However, this configuration has several disadvantages. For example, the area or slit between the counter bits tends to get clogged with debris from the splitting and crushing procedure, particularly at the base section of the slit. This clogging requires that the apparatus be shut down and the slit cleared from time to time during the splitting and crushing procedure. It is also possible that rocks coming up with stump roots may penetrate or lodge in the slit between the counter bits thereby causing damage to the counter bits. Additionally, the arcuate design of the bits can be problematic when replacing dulled bits. Further, unless the pivotable bit is manufactured such that it aligns precisely with the slit between the counter bits, damage to the apparatus is very possible.
U.S. Pat. No. 5,080,151 to Pallari describes a tree stump lifting and crushing apparatus comprising one or more lifting hooks and a bit which is pivotable and turnable against a counter bit for crushing tree stumps placed therebetween. The pivotably closable bit and counter bit include a cutting surface and a counter surface. The counter surface is substantially continuous and extends across the width of the cutting surface upon closing of the bits. A closure stop means is provided that is intended to prevent destructive engagement of the cutter surface and counter surface.
Though somewhat of an improvement over the prior art, serious problems were encountered by this apparatus. For example, effectively securing the tree stump during the lifting and crushing procedure remained problematic. Additionally, the area or slit existing between the stump hooks invited the same debris and clogging as the devices of the prior art. Consequently, similar limitations were observed in terms of down-time and potential for damage to the apparatus.
Another device is described in U.S. Pat. No. 5,636,802 to Tagawa. That device comprises a pair of arms which are substantially identical in configuration and which are rotatably supported attached to a support structure. The Tagawa device is not capable of dual pivot movement due to a limitation in its configuration. Specifically, an arm drive mechanism simultaneously actuates rear ends of the paired arms, thus functioning similar to a single pivot device. Further, the Tagawa device is specifically constructed for demolition of concrete and other structures, e.g., wooden houses. In practical terms, such structures have reduced thicknesses of about one foot. Such a configuration is ill suited for other work products having greater thicknesses, such as tree stumps and the like. Notable disadvantages of using the Tagawa device on such work products include forward slippage and limited power (force) when the arms are in an open position during the crushing operation.
There remains a need for an apparatus to securely lift, excavate, split and crush tree stumps that avoids the various problems of the prior art. Specifically, it would be highly desirable to develop a tree stump lifting and crushing apparatus that would offer an increased holding area for the grabbing and subsequent handling of the tree stump during the cutting process. It also would be highly desirable to develop a tree stump lifting and crushing device that could securely hold the tree stump during the cutting process such that forward slippage of the stump would be prevented. It also would be highly desirable to develop a tree stump lifting and crushing device that would avoid the inherent limitations associated with the devices of the prior art that have a stationary jaw configuration. It also would be highly desirable if such a device could offer maximum power in an open configuration for more effective crushing. Further, it would be highly desirable to develop a tree stump lifting and crushing device that would avoid the debris and clogging problems seen in the devices of the prior art.
The present invention provides an apparatus that can lift, excavate, secure, split and/or crush tree stumps, as well as other materials, particularly other wooden materials. The apparatus is characterized in part by a two pivot point design. In a preferred design, a first pivot point assembly allows for the pivotable operation of an engaging unit which can grab and lift the tree stump. A second pivot point assembly allows for the pivotable operation of a cutting device which facilitates splitting and crushing of the stump.
The novel design of the present invention provides significant advantages over the devices of the prior art utilizing a single pivot point system. For example, the multiple pivot design of the present invention permits a significantly increased holding area for the tree stump or other object during the excavating and crushing process. Additionally, this increased holding area provides better mechanical advantages in general, as the engaging unit and cutting device can be retracted to open wider to accommodate larger tree stumps. This larger, wider opening is particularly useful when grabbing the tree stump at the outset of the excavation process. Further, the novel configuration of the present invention provides a crushing device which offers maximum power when the engaging unit and cutting or grappling devices are in an open position.
In preferred designs, the engaging unit and cutting or grappling devices are independently, pivotably and opposedly connected to a lower end of an arm-like supporting structure. An upper end of the supporting structure is attached to a hydraulically powered, manipulatable boom such as a bucket arm of a digging machine, crane or the like.
The supporting structure suitably comprises two reinforcing side plates, sometimes referred to herein as xe2x80x9csticksxe2x80x9d, with a stick backplate disposed therebetween. The supporting structure has a wider diameter at its lower end. This design provides additional reinforcement to the supporting structure during the splitting and crushing process and avoids destructive engagement of the engaging unit and cutting device.
In a preferred embodiment, a plurality of anchor hooks protrude from each of the outer surfaces of the reinforcing side plates of the supporting structure. The anchor hooks provide a means of securing a first and second reinforcing member on either side of the two reinforcing side plates. Typically, one end of the reinforcing member is mounted to the anchor hooks; the other end is secured below, at the pivot point assemblies. This novel aspect of the present invention provides additional support, strength and durability to the apparatus during the tree lifting and crushing operation. Further, this design provides significant ease of operation in terms of mounting and dismounting attachments relative to an excavator.
In an alternate preferred embodiment, the reinforcing members are secured to the supporting structure using a plurality of clamps.
The engaging unit preferably comprises two side plates and a backplate securely disposed therebetween. In a preferred embodiment, each side plate has a spear-like extension which protrudes from a leading edge of the side plate to facilitate grasping and/or securing of the tree stump during the lifting and crushing process. The planar design of the engaging unit""s backplate does not invite any clogging or debris from the stumps being cut. Therefore, opportunity for damage to the apparatus associated with clogging or debris and downtime associated therewith are substantially eliminated.
In an alternate preferred embodiment, the engaging unit may further comprise an attachment, e.g., a rake or a blade. Using such a configuration, the engaging unit can perform an additional function without disrupting the excavating and cutting operation.
The cutting device preferably has a curved, sharpened outer surface referred to herein as a knife blade. In a preferred embodiment, a similarly curved, elongated knife tooth is mountably attached to the knife blade. A knife tooth plate is disposed between the two sides of the knife tooth and provides reinforcement and strength to the cutting device structure during operation. The knife tooth and knife tooth plate may be removed, sharpened and replaced as necessary. In an alternate aspect of the invention, a grappling unit is used in place of a cutting unit. In a particularly preferred aspect, a grappling unit may be removably attached to the cutting unit whereby a single apparatus can be readily outfitted for splitting/crushing objects (with use of the cutting unit) as well as lifting and transporting objects (with use of the removable grappling unit).
On one side of the supporting structure, a first hydraulic cylinder connects the reinforcing member to a rear portion of the engaging unit. On the other side of the arm-like supporting structure, a second hydraulic cylinder connects the reinforcing member to a rear portion of the cutting device. Using hydraulics controlled from the cab of the digging machine, the two hydraulic cylinders are retracted to facilitate movement and communication of the engaging unit and cutting device during the tree lifting and crushing process.